Fix SmartTube “Unknown source error – Response code: 403”

Update March 25, 2025: The solution shown here also works for the currently occurring 403 error in SmartTube!

SmartTube is an ad-free YouTube alternative for smart TVs with Google TV or Android TV, Google TV Streamer, Chromecast or Amazon FireTV sticks. Many people have become used to being able to watch videos without ad breaks – but from time to time there are problems with SmartTube: videos can no longer be played and a 403 error appears. Find out more about the background and how you can easily fix the problem.

Notice:
This is a translation of the German article. Please note that especially menu names, button labels, names, screenshots etc. might not be translated (correctly). Feel free to let us know in the comments if you notice any errors.

Error

At first glance, everything seems to be normal with the SmartTube app: Subscriptions, channels, search results and thumbnails load without any problems. However, as soon as you click on one of the videos, one of the following error messages appears and the video cannot be opened.

• Unknown error - Response code: 403
• Unknown source error - Response code: 403...

The error refers to the HTTP status code 403, which means “access denied” or “forbidden” and indicates that access to the requested resource has been blocked by the server.

Reason

Since SmartTube connects to the YouTube servers and Google (operator of YouTube) makes changes to the infrastructure now and then, such 403 errors occur from time to time and can have different causes. Here are a few notes on current and past errors:

• It is generally worth searching the GitHub issues to find information about current 403 errors.
• March 24, 2025: see among others GitHub Issue #4467
• July 9, 2024: Google has “suddenly” introduced an anti-bot check, which after its introduction has not then been implemented by SmartTube and other YouTube alternatives. Therefore, there are many comments and complaints about the bug in SmartTube’s GitHub issues (see e.g. #3606).
  Further information can be found at Heise (German), among others.

Solution

The developers of SmartTube usually react very quickly with updates to fix 403 errors. Thanks to the update mechanism integrated in SmartTube, the solution is very simple: Wait for an update to become available and then update SmartTube. You can follow these instructions on how to do this. After the update, the error 403 has disappeared and the videos can be played again as usual.

• March 24, 2025: There are three updates that fix the current error “Unknown source error – Response code: 403…”: Versions 26.93, 26.95 and 26.96 (as of March 26, 2025)
• July 9, 2024: At least five versions have been released that affect the 403 error: Versions 22.36, 22.38, 22.39, 22.43 and 22.44, some of which contain temporary fixes for the different video resolutions. (as of July 19, 2024)